Alter Tive Feed as a Means of Reducing Damage to Direct Sown Rice by the Oriental Turtle Dove, Streptopelia Orientalis

27 Mar Alter Tive Feed as a Means of Reducing Damage to Direct Sown Rice by the Oriental Turtle Dove, Streptopelia Orientalis

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Abstract

近年, 農作業の省力化のために, 水稲の直播栽培が各地で行われているが, 播種期の鳥害が問題となっている. 入水前の田にモミを播く乾田直播ではキジバトStreptopelia orientalisが播種後に集団でモミを採餌するために, 地域によっては大きな被害を出している. そこで本研究では野外大網室内の実験水田において, 大麦を用いた代替餌場を設置することにより, キジバトの水稲への被害を軽減できるかどうかを実験した. 実験は代替餌設置区と非設置区とを設け, キジバトの導入時期は前期 (播種直後から出芽揃い) と後期 (出芽揃い以降に前期と同じ期間) に分けた, 代替餌の有無と導入時期の組み合わせの2×2の4処理を1セットとし, 2000年5月1日から9月12日にかけて5セット繰り返した. 苗立ち数を処理区とキジバトが入れないようにしたエクスクロージャーとの間で比較したところ, 前期では代替餌設置区で有意差がなく, 代替餌非設置区で有意に少なかった. 一方, 後期の苗立ち数は代替餌のあるなしに関わらず, エクスクロージャーとの間に有意差はなく, 出芽揃い以降には被害が生じないことが示された. これらのことより被害の時期は播種から出芽揃いの時期であること, 代替餌の設置により被害が軽減されることが明らかとなった.

English Abstract

Direct sowing of rice is increasing in Japan as a means of reducing farm labor. Seed damage by birds, including the Oriental Turtle Dove Streptopelia orientalis, has, however, prevented the spread of direct sowing. An experiment with five replications was conducted from 1 May to 12 September 2000 in an outdoor aviary, in order to determine whether damage by Oriental Turtle Doves could be reduced by providing barley as an alter tive feed. The aviary was divided with nets into four plots and assigned to four treatments of 2×2 about feed provision and experimental period. In the experiment, alter tive feed was either “provided” or “not provided”, while during the experimental period, treatment were assigned as either “early” (doves were introduced into a plot right after the sowing and kept there until germi tion) or “late” (doves were introduced on the day of germi tion and kept there for the same number of days as in the “early” treatment). Damage was evaluated by comparing the number of seedlings with that in exclosures set inside the plots. In the “early” treatment, the number of seedlings in the alter tive feed treatment did not differ from that in the exclosures, but in the non-alter tive feed treatment, the number of seedlings was significantly fewer than that in the exclosures. In the “late” treatment, the number of seedlings did not differ from that in exclosures irrespective of alter tive feed provision, suggesting that damage did not occur after germi tion. These results showed that damage by doves ceases at germi tion, and can be reduced by providing alter tive feed.